1. Field of the Invention
The present invention concerns eyeglass frames and especially frames in which the rims or surrounds are at least in part made from a relatively rigid material such as a metal or an alloy, for example.
2. Description of the Prior Art
It is usual in this case for the rims or surrounds to have a U-shape cross-section with a median part and side flanges to hold the mineral or organic lenses over at least part of their length.
This is the case in French patent No 1 281 449, for example.
These metal eyeglass frames have the advantage of being very thin. The overall outside thickness of their visible part, that is to say of their rims or surrounds, can advantageously be made small because of the stiffness of the material from which they are made.
Whether these rims or surrounds are complete, i.e. made from a relatively rigid material over all of their length, closing by means of a lug onto the lenses that they enclose, or partial, i.e. only a portion of their length is made from a relatively rigid material, running along the top or bottom of the lenses, with a metal or synthetic material filament completing them below or above the lenses, the problem arises of matching the lenses to the contour of the relatively rigid material portion.
Failing such matching, there is the risk that the lenses will be insufficiently securely retained with the result that they may rotate or even drop out, or the risk of localised excessive clamping of the lenses which may damage them, for example cause them to chip.
To counter this risk it was proposed many years ago to associate with each rim or surround a strip of relatively flexible material adapted to be disposed radially between the rim or surround and the respective lens, along the edge of the latter, with the advantage of preventing any contact between the lens and the rim or surround.
This is the case in French patents Nos 1 551 484 and 2 467 417, for example.
To retain the relatively flexible material strip the strip and the associated rim or surround have complementary shapes.
At present this means that in practice the median part of the U-shaped profile of the rim or surround must be made thinner, at least in a localised area, to form a groove in which a complementary rib on the strip of relatively flexible material is engaged. This is the case in French patents Nos 1 551 484 and 2 467 417.
Being made thinner and therefore weaker in its median part, the U-shape profile of a rim or surround of this kind can tend to open like a hinge, for example if loads are applied to the side flanges. These loads are not necessarily the same on both flanges.
As previously, this can result in insufficiently secure retention of the lenses and even their possible loss.
A general object of the present invention is an arrangement whereby this problem is circumvented.